Centrifugal governor for electric motor



July 4, 1967 VON 55cm x O I 3,329,878

CENTRIFUGAL GOVERNOR FOR ELECTRIC MOTOR Filed April 14, 1964 INVENTOR PAUL VON ESCH I United States Patent CENTRIFUGAL GOVERNOR FOR ELECTRIC MOTOR Paul von Esch, Ritterstrasse 6, Zurich, Switzerland Filed Apr. 14, 1964, Ser. No. 359,739 Claims priority, application Switzerland, Apr. 16, 1963,

4,766/63 6 Claims. (Cl. 318-325) ABSTRACT OF THE DISCLOSURE A centrifugal governor for the shaft of an electric motor, comprising a plate perpendicular to the axis of rotation of the shaft and carrying a U-shaped leaf spring lying in the plane of the plate and affixed thereto with weighted resilient arms extending along opposite sides of the plate. The arms are centrifugally spreadable away from the sides of the plate and co-operate with contact means thereon for controlling the angular velocity of the shaft. An outer U-shaped member lies in this plane outwardly of the leaf spring and reaches around the bight thereof for biasing the arms with respect to the plate. The governor also includes an impedance operating with the contact means and connectable in circuit with a-winding of the motor upon deflection of at least one of the arms.

My present invention relates to centrifugal governors adapted to be mounted upon a rotatable member and, more particularly, to relatively compact centrifugal governors suitable for use in electric motors or the like.

While it is well known to provide centrifugal governors for rotatable members such as the shafts of electric .motors, engines and the like, these governors being adapted mechanically or electrically to control their source of motive power, in general earlier governors have been characterized by complexity of construction and considerable bulk. It has long been a quest in this field to provide a centrif. ugal governor of relatively small axial extent which nevertheless would act positively and effectively to regulate the speed of the member upon which it is mounted. Heretofore, such governors have included weighted arms or other devices pivotally mounted upon a rotatable member, such as a shaft, and swingable generally in axial planes to operate a brake, clutch or switching device adapted to modify the. speed of the rotatable member. Centrifugal governors of this type had a considerable axial extent and were difficult to control. Other centrifugal governors have made use of arrays of weights adapted to shift radially outwardly and co-operate with contact means for modifying and electric circuit. In such constructions, it was also difficult to regulate the operation of the governor in such manner that the contacts would close or open only at a predetermined speed and to adjust the predetermined speed of switchover.

It thus has been a considerable problem to obtain heretofore centrifugal governors of relatively short axial length for use in small electrical motors for devices in which constant speed is required. Devices of the type where such governors are required include tape recorders, dictating machines, phonographs and the like.

It is, therefore, the principal object of the present invention to provide a centrifugal govern-or for rotatable members having a relatively small axial length.

A further object of the present invention is to provide an improved centrifugal governor for electric motors, e.g. those suitable for use in tape recorders, dictating machines and phonographs, which is both compact and eflicient in operation while being of relatively simple and inexpensive construction.

Still another object of this invention is to provide a ice motor of the character described having an improved centrifugal governor adapted to regulate this speed.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by providing a centrifugal governor for a rotatable member, such as the shaft of an electromotor, which comprises a generally U-shaped leaf spring whose bight portion is rigidly secured to a support and whose resilient arms are weighted so that ro ation of the member and the support deflects these arms outwardly under the effects of centrifugal force. The U-shaped leaf spring rotates about an axis transverse to its plane and has a relatively small axial extent compared with the length of the arms. At least one of the resilient arms of the U-shaped spring is, according to a more specific feature of this invention, provided with contact means engageable with a complementary contact means upon its support, the contacts being preferably connected in circuit with an energizing winding of the electrical motor, of which the rotatable member forms a part, to regulate the speed of the rotatab-le member. If the electr-omotor is provided with braking windings, the contact means can be normally open and closa ble upon deflection of the arms beyond a predetermined point to activate the braking windings; more generally, however, the contacts are normally closed and are connected in circuit with one or more energizing windings of the motor, so that upon the attainment of an angular speed in excess of the predetermined level, the resilient arms open the contacts and de-energize the corresponding motor windings or reduce their activation currents. Advantageously, both arms of the U can be provided with respective contacts connected in circuit with respective branches of the energizing windings; respective impedance means, such as ohmic resistors, bridge the sets of contacts so that, when the contacts are opened, the shunt impedances reduce the current flow to the respective branches of the windings.

According to a more specific feature of the present invention, the resilient arms are provided with weights at intermediate locations between the bight portion of the U and the free extremities of the arms, the respective contacts being provided at these free extremities. The support means for the U can include a flat element adapted to fit within the U and lying in the plane thereof while carrying the countercontacts co-operating with the contacts of the arms. This inner element can be constituted as a plate upon which the impedance means mentioned above can be mounted, the U being secured to this plate at its bight portion.

In addition to the support plate of electrically insulating material, the support means can include an outer U shaped member or shackle which lies in the plane of the U and reaches around its bight portion with shanks extending generally along the arms of the U-shaped spring but spaced outwardly from these arms. Advantgeously, the shanks of the support shackle can be provided with adjusting means, e.g. screws, for controlling the pressure at which the arms of the U are held against the support plate and thus the centrifugal force required to open the contact. The screws thus also provide an adjustment of the angular velocity at which the switch contacts are tripped as described above. The adjusting means of the outer support member can bear upon the arms of the U at a location intermediate the bight portion thereof and the weight carried by these arms. Since the arms tend to bend ,away from their bight about a fulcrum formed by the adjusting means, it is desirable to provide some form of positive stop for the centrifugally displaceable weights so that the elastic limit of the spring will not be exceeded in the event the motor overspeeds by considerable extent. For this purpose, the free extremities of the shanks Patented July 4, 1967 of the shackle can be positioned adjacent the weights to serve as stops therefor.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the appended drawing in which:

FIG. 1 is an end view, taken in an axial direction of a centrifugal governor for a diagrammatically illustrated electrical motor;

FIG. 2 is a side-elevational view of the motor and the governor carried thereby;

FIG. 3 is a perspective view of the U-shaped leaf spring of the governor of FIGS. 1 and 2; and

FIG. 4 is a circuit diagram for the motor of FIG, 2.

In FIGS. 1-3, I show a centrifugal governor which is mounted upon the shaft 1 of .a small electric motor of the type which can be incorporated in a phonograph, dictating machine or tape recorded. The governor comprises a support means including a generally fiat, rectangular plate 2 of electrically insulating material which is mounted on a shaft 1 for entrainment thereby, the plate being rotatable in a plane transverse to the axis of the shaft 1. At the shorter side of plate 2 (lower side in FIGS. 1 and 2) a U-shaped supporting shackle 4 is mounted in the plane of plate 2 and outwardly of a U-shaped leaf spring 5 via a single screw 3 passing through the bight portions of the shackle 4 and the leaf spring 5. The arms 5' of the leaf spring 5 extend along the longer sides of plate 2 and are each provided with a respective contact rivet 9 of rounded configuration as illustrated in FIG. 3. Contacts 9 cooperate with countercontacts 8 formed by flat rivets received in the flanged terminals 7 mounted at the upper extremity of the plate 2 (FIG. 1) and afiixed thereto via screws 6. The contact rivets 8 of the bent terminal tongues 7 overlie the longitudinal edges of the plate 2 and thus are juxtaposed with the arms 5' of leaf spring 5. As illustrated in FIG. 3, the U-shaped leaf spring 5 is provided with an .aperture 10 through which the screw 3 passes and, at intermediate locations along the arm 5, with weights 12 riveted onto the arms. The bight portion of the U-shaped leaf spring 5 is formed integrally with a soldering lug 11. The shanks of the shackle 4 carry respective adjusting screws 13 for regulatin the magnitude of the force or load which the arms 5' are resiliently held against the countercontacts 8, The higher the inward force or pressure, the higher will be the angular velocity which must be attained in order to disengage or open the contacts. The free extremities 4 of shackle 4 form stops for the Weights 12 which tend to bend in the direction of these abutment surfaces when the shaft 1 is subjected to an excessive angular velocity as may occur when the motor is connected to a source of voltage greater than that at which the motor is rated.

From FIGS. 2 and 4, it can be seen that the motor includes a plurality of angularly spaced pole pieces 15 mounted upon the armature 18 and provided with respective windings 16 and 16', the former being common to both of the latter when the pairs of contacts 8, 9 are closed. The iar-mature c-o-operates with the stator poles 19, which can constitute part of a bipolar permanently magnetized ring not further illustrated. Resistors 14, carried by plate 2, shunt the respective pairs of contacts 8, 9 and constitute high-impedance paths for the energizing current which is supplied to the commutator 17 via the brushes 20 from the energizing source. It will be apparent that, when the pairs of contacts 8, 9 are closed, each branch winding 16' is connected in series with the main winding 16 for selective energization via the armature segments to which these windings are connected. The motor is thus fully energized and operates at its high speed. Should the speed be excessive, however, contacts 8, 9 open so that the high-impedance paths 14 are connected in the respective winding circuits and the energizing current is thereby reduced to slow the motor down. While the circuit of FIG. 4 is preferred because it permits the contacts 9 of the U-shaped member 5 to be electrically connected with one another, other circuits for controlling the motor made via the governor can also be employed.

The invention as described and illustrated is believed to admit of many modifications and variations within the ability of persons skilled in the art, all such modifications and variations being deemed to be included within the spirit and scope of the appended claims.

I claim:

1. A centrifugal governor for a rotatable member driven by an electric motor having at least one energizing winding, comprising support means carried by said member and rotatably entrained thereby about an axis, said support means including a plate rotatable in a plane transverse to said axis; a generally U-shaped leaf spring lying in said plane and affixed to said plate, said leaf spring having a pair of weighted resilient arms extending along opposite sides of said plate and centrifugally defiectable in said plane outwardly from said sides; co-operating contact means on said plate and at least one of said arms connected in circuit with said energizing winding for regulating the angular velocity of said member, said support means further including an outer U-shaped member lying in said plane outwardly of said leaf spring and reaching around at least the bight thereof while being aiiixed to said plate; adjusting means on said outer member for selectively biasing said one of said arms in the direction of said plate; .and impedance means bridging said contact means for connection in circuit with said winding upon outward deflection of said one of said arms to disengage said contact means from one ,another.

2. A centrifugal governor as defined in claim 1 wherein said plate is composed of an electrically insulating material.

3. A centrifugal governor as defined in claim 2 wherein said bight of said leaf spring is provided with a terminal for connecting said leaf spring in circuit with said winding.

4. A centrifugal governor as defined in claim 1 wherein said arms are provided with weights projecting outwardly therefrom and said outer U-shaped member is disposed in engaging relationship with said weights upon excessive outward deflection of said arms for providing positive stops therefor.

5. A centrifugal governor as defined in claim 1 Wherein said adjusting means includes a pair of adjusting screws, each engaging one of said arms at a location intermediate the bight of said leaf spring and the free extremities of said arms, said arms being weighted at a location intermediate said screws and said free extremities.

6. A centrifugal governor as defined in claim 5 wherein the contact means on said one of said arms is disposed at the free extremity thereof.

References Cited UNITED STATES PATENTS 2,523,298 9/1950 Haydon 318-311 2,830,205 4/1958 Castagna 200 X 2,840,773 6/1958 Kavanaugh et a1. 318-311 3,058,017 10/1962 Haydon et al 318-311 X 3,187,126 6/1965 De Barba 318311 X ORIS L. RADER, Primary Examiner.

J. BERENZWEIG, J, J. BAKER, Assistant Examiners, 

1. A CENTRIFUGAL GOVERNOR FOR A ROTATABLE MEMBER DRIVEN BY AN ELECTRIC MOTOR HAVING AT LEAST ONE ENERGIZING WINDING, COMPRISING SUPPORT MEANS CARRIED BY SAID MEMBER AND ROTATARY ENTRAINED THEREBY ABUT AN AXIS, SAID SUPPORT MEANS INCLUDING A PLATE ROTATABLE IN A PLANE TRANSVERSE TO SAID AXIS; A GENERALLY U-SHAPED LEAF SPRING LYING IN SAID PLANE AND AFFIXED TO SAID PLATE, SAID LEAF SPRING HAVING A PAIR OF WEIGHTED RESILIENT ARMS EXTENDING ALONG OPPOSITE SIDES OF SAID PLATE AND CENTRIFUGALLY DEFLECTABLE IN SAID PLANE OUTWARDLY FROM SAID SIDES; CO-OPERATING CONTACT MEANS ON SAID PLATE AND AT LEAST ONE OF SAID ARMS CONNECTED IN CIRCUIT WITH SAID ENERGIZING WINDING FOR REGULATING THE ANGULAR VELOCITY OF SAID MEMBER, SAID SUPPORT MEANS FURTHER INCLUDING AN OUTER U-SHAPED MEMBER LYING IN SAID PLANE OUTWARDLY OF SAID LEAF SPRING AND REACHING AROUND AT LEAST BIGHT THEREOF WHILE BEING AFFIXED TO SAID PLATE; ADJUSTING MEANS ON SAID OUTER MEM- 